The invention relates to weft insertion systems for use in travelling-wave looms, and more particularly to an endless-chain arrangement for feeding a plurality of weft threads from a plurality of bobbins to the individual weft inserters.
In known systems of this type, a first endless chain carries a plurality of spaced weft inserters around an elongated path that is curved at both ends, and a second endless chain carries a plurality of winding units around an oval path coinciding at one end with the curvature of the end path of the first chain. The winding units are individually adapted to present weft threads from an associated plurality of bobbins to the successive weft inserters during simultaneous movements of the first and second chains.
Typically, the oval path of the second chain is defined by a guiding surface of an elliptical track. A common drive member is coupled in parallel to a pair of spider elements, which engage a length of the first and second chain to ideally drive them in synchronous relation.
In practice, several disadvantages have manifested themselves with respect to the second chain, both with regard to its manner of driving by the common drive means and with regard to the mounting thereto of the associated winding heads. In particular, because of the relatively imprecise region of contact of the spider member and the successive links of the second chain, the second chain tends to move out of phase with the first chain the which it is ideally synchronized. This, in turn, leads to stresses and breakage of the weft threads. Additionally, in such arrangements the individual winding heads are affixed to the second chain via the elongated pins that interconnect the successive links of such chain. As a result, replacement and exchangeability of the winding heads is extremely difficult.
Another disadvantage of such prior art arrangements is that the adherence of the second chain to the guide surface of the associated oval track is accomplished solely by rollers disposed on the chain on one side of such track. The resulting small contact surface between the chain and the track results in instabilities during the movement of the second chain, and further contributes to stresses and breakage of the weft threads.